<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <!-- 使用函数完成任意数字阶乘的计算 -->
    <script>
        var randomNumber=parseInt(prompt("请输入一个数字"))
        function num(b) {
            var total=1;
            for (var i = 1; i <=b ; i++) {
                total *= i
            }
            alert("该数字的阶乘结果为"+total);
        }
        num(randomNumber);
    </script>
</body>

</html>